Embodiments presented herein relate generally to an electric power system and more particularly relate to devices for the electric power system.
Electric vehicles have attracted much attention recently. Electric vehicles are generally propelled by electric motors powered by a battery pack. The battery pack of an electric vehicle frequently needs to be recharged as the charge stored within the battery pack is repeatedly drawn down through normal use of the electric vehicle. Such charging and recharging of electric vehicles poses technical challenges for traditional electric power systems.
Traditional electric power systems are generally provided with protection features for protecting customers and equipment from a “fault”. A fault condition may occur as a result of overly high current flowing through the electric power system resulting from a power line touching the ground. This high current may cause damage to equipment and is a potential hazard for people exposed to the fault. Electric power systems are generally provided with protection devices such as circuit breakers and reclosers, for isolating the fault condition within the electric power system. These protection devices are deployed at substations and throughout the electric power system. A circuit breaker is a switch that trips, or opens, when the device detects a high fault current transmitted through the electric power system. A recloser is essentially a programmable circuit breaker device that is used to isolate faults within an electrical power system. The operation of protection devices is based on the currents and voltages transmitted through the electric power system. If the current transmitted through the electric power system is higher than a predefined threshold limit, the protection devices may infer that a fault has occurred and may operate to isolate the fault. When a protection device isolates a fault, it means that customers downstream of the device will lose power until service is restored. The protection devices may be programmed to operate at a predefined threshold limit. Generally, the protection devices are programmed with time-current characteristics. The time-current characteristics govern the operation of the protection devices. For example, the time-current characteristics of a protection device may be designed such that a high fault current may cause the protection device to take a faster corrective measure, while a low fault current may result in slower operation of the protection device.
In normal operation, the charging of electric vehicles may draw a large current from the electric power system. Since electric vehicles are mobile, the charging of these vehicles may take place at random geographic locations and random times within the electric power system. Accordingly, a protection device with pre-programmed time-current characteristics may not be able to support the dynamic power requirements arising out of the charging of electric vehicles. For example, the charging of a large number of electric vehicles located in a specific area or zone may appear as a fault to a pre-programmed protection device. Traditional electric power systems do not distinguish between a high current due to increased load and a high current due to a fault. This may result in unnecessary power outages throughout the electric power system.
There is a need for systems which may adapt dynamically according to the power requirement from the grid.